So siehts ganz gut aus !

node_modules/es5-ext/date/valid-date.js

@@ -0,0 +1,8 @@
+"use strict";
+
+var isDate = require("./is-date");
+
+module.exports = function (value) {
+	if (!isDate(value)) throw new TypeError(value + " is not valid Date object");
+	return value;
+};